Electro-optic (EO) systems are generally integrated with higher level systems that provide various functions such as navigational and/or targeting capabilities. An EO system typically comprises several optical subsystems or devices each of which transmits and/or receives light along an optical axis. For example, an EO system in the form of a multispectral forward-looking infrared (FLIR) system may have several subsystems including, for example, an IR imaging device, a laser rangefinder, a laser designator and a visible CCD camera. To provide reliable operation, the optical axes of the subsystems must be accurately aligned relative to each other and to a reference axis that can be related to the higher level system in which the EO system is to be used.
Alignment of the optical axis of an optical device has been traditionally performed by making mechanical boresighting adjustments. For example, in U.S. Pat. No. 3,628,868, a laser boresighting device is disclosed that provides alignment by means of manual micrometer adjustments. However, the accuracy of such adjustments can be adversely affected by backlash or human error, among other factors. A laser designator system utilizing automatic mechanical adjustments to achieve alignment is disclosed in U.S. Pat. No. 4,155,096. The adjustments are made in response to the movement of a gimbaled mirror. However, the alignment accuracy is limited by the accuracy with which the gimbaled mirror can be mechanically positioned, which may be affected by vibrations or other extraneous disturbances.